In various applications, a broadband antenna that can be integrated into a vehicle or other structure is required. For example, a broadband antenna for integration into the vertical stabilizer of an aircraft must essentially be a two-dimensional structure. This creates challenges for the antenna designer, particularly in view of the broad bandwidth requirements that may also apply.
In order to provide broadband performance in an essentially two-dimensional structure, previous designs have utilized dipole elements on one side of a substrate, with capacitive feed structures on the opposite side of the substrate. In such designs, coupling between dipoles is achieved through edge coupling. This requires extremely small gaps, a very thin substrate, dipole elements that are open in the center, and precision manufacturing techniques. Accordingly, such designs can be expensive to produce. In addition, the efficiency of such designs may be less than desired.